The term “functionalization” and related terminology are used in the art and herein to refer to the process of treating a material to alter its surface properties to meet specific requirements for a particular application. For example, the surface energy of a material may be treated to render it particularly hydrophobic or hydrophilic as may be desirable for a given use. Thus, surface functionalization has become common practice in the manufacture of many materials because it adds value to the end product. In order to achieve such different ultimate results, functionalization may be carried out in a variety of ways ranging from wet chemistry to various forms of vapor deposition, vacuum metallization and sputtering.
Some examples of functional materials include hydrophilic materials, including monomers containing one or more of hydroxyl, carboxyl, sulphonic, amino, or amido functional groups; hydrophobic materials, including monomers or sol-gels containing a fluorinated functional group, or monomers or sol-gels comprising a hydrophobic nanostructure; antimicrobial materials, including monomers or sol-gels comprising an antimicrobial functional group, an encapsulated antimicrobial agent, a chlorinated aromatic compound, or a naturally occurring antimicrobial agent; fire-retardant materials, including monomers or sol-gels comprising a brominated functional group; self-cleaning materials, including photo-catalytically active chemicals, a metal oxide; zinc oxide, titanium dioxide, or tungsten dioxide; ultraviolet protective materials, including titanium dioxide; and, acrylic polymers.
The term “superhydrophobic” is known in the art, and includes a material property whereby the contact angle of a water droplet is extremely high, for example, exceeding 150°.
The term “superhydrophilic” is known in the art, and includes a material property whereby the contact angle of a water droplet is extremely low, for example, approximately 0°.
The term “wicking” is known in the art, and includes a material property whereby moisture is transported into a fabric or other material by capillary or other action.
Various types of composite materials are known in the prior art.
Unfortunately, these materials have a number of deficiencies making them less suitable for incorporation into apparel, particularly in their thermal properties, moisture management, water repellency, and durability.
For Example, U.S. Pat. No. 5,955,175 to Culler describes a textile material produced by metalizing a microporous membrane. The metallization causes a reflection of thermal radiation. The metal forms a discontinuous layer on the surface and on the pore walls of the microporous membrane that are adjacent to the surface. Compared to the size of water molecules, the pores of the microporous membrane are very large, even in the metalized state, so that the water-vapor permeability of the microporous membrane is maintained even after it is metalized.
These fabrics are both air permeable and moisture vapor permeable after being metalized and coated with an oleophobic coating. However, the microporous membranes are considerably less durable than monolithic non porous counterparts, particularly in outdoor apparel applications and in salty environments.
Water-vapor-permeable, watertight, and heat-reflecting composites made from a metal layer and a nonporous substrate, have been disclosed in U.S. Pat. No. 6,800,573 to Van de Ven, et al., where metalization takes place using vacuum plasma cleaning and vapor deposition onto the nonporous substrate which is a membrane adhered to spaced apart textile filaments.
However, no coating is applied between the substrate and the metal layer thereby leaving the metal layer vulnerable to oxidization. In Van de Ven et al, the water-vapor-permeable membrane itself is metalized, which creates manufacturing and durability problems, and compromises the moisture permeability of the membrane compared to its original non-metalized state.
In the present invention a textile with appropriate moisture management is metalized prior to lamination to the membrane, which has the added benefit of improving the moisture wicking, permeability, and breathability of the composite laminate material, as well as improving the durability and insulation of the metallization from conductive heat loss. The metallization can also be sandwiched between the water-vapor-permeable membrane and supporting fabric which helps to insulate the conductive nature of the metallization from heat transfer via convection. The present invention also possesses advantages in manufacturing and logistics whereby a single metalized textile may be used in a range of different composites materials.
U.S. Pat. No. 4,999,222 to Jones et al. describes moisture vapor permeable metalized polyethylene sheets with low emissivity prepared by calendaring a plexifilamentary film-fibril sheet followed by vacuum metallization. U.S. Pat. No. 4,974,382 to Avellanet describes an infiltration and energy barrier that can be vapor permeable or impermeable having at least one metalized layer thereon. Published PCT International Application No. WO 01/28770 to Squires et al. describes breathable building membranes that include an under layer of microporous film and a top layer formed of a filamentous polymeric fabric, for example a spun bond fabric, which is provided with a moisture vapor permeable reflective metal coating.
While the breathable metalized substrates described above provide a thermal barrier by reflecting infrared radiation, they are susceptible to oxidation of the metal layer upon exposure to air and moisture. An oxidized metal layer generally has a higher emissivity than the corresponding metal and is less effective as a thermal barrier. In addition, the thin exposed metal layer can be damaged during processing and installation.
When the use of metallization to create infrared reflecting barriers is adopted for clothing or outdoor equipment such as sleeping bags or tents, corrosion, particularly in salty environments, of these metal layers through oxidization can be considerable and accelerated.
US Patent Application Publication US 2004/0213918 A1 (Mikhael et al.) discloses a process for functionalizing a porous substrate, such as a nonwoven fabric or paper, with a layer of polymer, and optionally a layer of metal or ceramic. According to one embodiment, the process includes the steps of flash evaporating a monomer having a desired functionality in a vacuum chamber to produce a vapor, condensing the vapor on the porous substrate to produce a film of the monomer on the porous substrate, curing the film to produce a functionalized polymeric layer on the porous substrate, vacuum depositing an inorganic layer over the polymer layer, and flash evaporating and condensing a second film of monomer on the inorganic layer and curing the second film to produce a second polymeric layer on the inorganic layer. Mikhael et al. also discloses another embodiment including the steps of flash evaporating and condensing a first film of monomer on the porous substrate to produce a first film of the monomer on the porous substrate, curing the film to produce a functionalized polymeric layer on the porous substrate, vacuum depositing a metal layer over the polymer layer, and flash evaporating and condensing a second film of monomer on the metal layer and curing the second film to produce a second polymeric layer on the metal layer. US Patent Applications US 2007/0166528 A1 (Barnes et al.) discloses a process for oxidizing the surface of a metal coating with an oxygen-containing plasma to form a synthetic metal oxide coating, to create resistance to corrosion of the metallized porous sheet.
However, these sheets, are micro-porous and less durable than other non-porous monolithic membranes known in the art.
It is therefore desired to provide composite garment materials which address these deficiencies.